Cerebral Redistribution

Cerebral redistribution is the diversion of fetal blood flow to the brain in response to hypoxia, shown by a low middle cerebral artery pulsatility index (below the 5th centile) or a low cerebroplacental ratio, also called brain sparing. It reflects placental insufficiency and chronic fetal hypoxia. It matters because it is associated with stillbirth, poor neurodevelopment, intrapartum distress and later cardiovascular disease, even when the fetus is not small.

• Common in late onset growth restriction.
• Risk factors: smoking, hypertension, preeclampsia, anaemia, malaria, advanced maternal age.
• It is an adaptation and not a sign of fetal safety.

Women are usually asymptomatic, with a small fundal height or reduced fetal movements in some. The diagnosis is made on Doppler.

• Small abdominal circumference in many.
• Normal heart rate pattern early on.
• Differential diagnosis: normal variation in the third trimester, constitutionally small fetus, growth restriction without hypoxia, fetal anaemia (raised velocity), technical error.
• Complications: stillbirth, intrapartum fetal distress, emergency caesarean section, neonatal acidosis, impaired neurodevelopment.

The approach is a Doppler set with growth assessment.

• Middle cerebral artery pulsatility index below the 5th centile, cerebroplacental ratio (middle cerebral to umbilical artery pulsatility index) below 1.08 or below the 5th centile.
• Umbilical artery Doppler, uterine artery Doppler, ductus venosus Doppler when abnormal.
• Estimated fetal weight, abdominal circumference, deepest vertical pocket, cardiotocography.
• Maternal tests: blood pressure, urine protein, full blood count, malaria rapid test, glucose.

The principle is delivery at 37 weeks, with closer surveillance and earlier delivery if other tests are abnormal.

• Supportive: daily fetal movement counts; left lateral rest; stop smoking; treat anaemia and infection; deliver in a facility with continuous cardiotocography.
• Pharmacological: ferrous sulphate 200 mg oral 8-hourly for anaemia; artemether-lumefantrine 4 tablets (each 20 mg and 120 mg) oral at 0, 8, 24, 36, 48 and 60 hours for malaria; labetalol 200 mg oral every 8 to 12 hours (maximum 2.4 g daily) or nifedipine modified release 30 to 60 mg oral once daily (maximum 120 mg) for blood pressure 140/90 mmHg or more; betamethasone 12 mg IM twice, 24 hours apart, if delivery is needed before 35 weeks; oxytocin 10 IU IM at birth.
• Procedures: induction at 37 weeks with misoprostol 25 micrograms vaginal 6-hourly (maximum 4 doses) or a Foley catheter with a 30 mL balloon, with continuous cardiotocography; earlier delivery for abnormal umbilical artery Doppler, abnormal ductus venosus, reduced movements or pathological cardiotocography; caesarean section for abnormal tracing.
• Red flags: reduced fetal movements, absent or reversed end diastolic flow, pathological cardiotocography, oligohydramnios, hypertension.
• Follow-up: Doppler weekly; cardiotocography twice weekly; growth scan every 2 weeks; newborn glucose check at 2 hours, with glucose below 2.6 mmol/L treated with dextrose 10 percent 2 mL/kg IV over 10 minutes then 80 mL/kg per day.